What is the geologic history of Mercury?
Mercury has some mysterious features that we can’t yet explain: Between its largest old craters are slightly younger plains. Many scientists believe these were created by ancient lava flows, but no one is certain. MESSENGER will send back information about events and forces that shaped the planet’s surface. Pictures of previously unseen portions of the planet (about 50%), will also be sent back to Earth. • What is happening in Mercury’s core? One of our surprises from the first mission to Mercury (Mariner 10) was that it has a global magnetic field. In fact, Mercury is the only terrestrial planet besides Earth to have one. Mercury’s magnetic field is weak, but the fact that it exists at all raises some interesting questions about what is happening deep inside the planet. MESSENGER will measure Mercury’s libration (the amount it “wobbles” as it spins on its axis), and its gravitational field to tell us about the size of the planet’s core and how much of it is solid. • What is the nature
